Bacterial attachment to their receptors, necessary to develop infection, occurs under intense mechanical perturbations. Bacteria colonizing the respiratory tract are adapted to attachment under mechanical stress caused by sliding mucus and coughing. Similarly, bacteria colonizing teeth have to resist brushing and chewing. Very few studies have addressed the role of mechanical forces on the attachment of bacteria because lack of appropriate experimental techniques and lack of knowledge on adhesive components in bacteria. This is especially true for Gram-positive organisms, which include many nasty pathogens. In this proposal, we aim to exploit increasing knowledge of Gram-positive adhesins. We will develop experimental methodologies based on light microscopy to study how Gram-positive pathogens attach to their receptors under mechanical perturbations. Understanding the basic principles of bacterial attachment in experimental systems resembling in vivo situation is the first step towards a new approach to fight bacterial infection, the long-term goal of this project. We will focus on the role of long, adhesive bacterial organelles called pili, which mediat initial interaction with target cells. We will characterize at the single-molecule level the mechanics of pilins, the building blocks of pili. We will develop physical models that explain bacterial attachment under force from mechanical properties of pili. We will search molecules that interfere with the mechanical behavior of pili and test if they are able to alter bacterial attachment under mechanical perturbation. Collaboration with world expert in pili, Prof. Ton-That, will be key to the proposal. The candidate needs additional training to acquire specific research skills and to foster career development. This proposal is designed to help the candidate to become a productive, independent scientist in Academia, with a research program focused on basic problems in Biology with relevance for disease such as the mechanics of Gram-positive pili. That is the long-term career goal of the candidate. Columbia University provides an outstanding scholar environment to acquire relevant research skills through interaction with relevant Faculty and the possibility to attend specialized courses. Also, the candidate will participate in career development seminars, including Responsible Conduct of Research events, which are organized by Columbia University aimed at training successful, independent investigators. Prof. Julio Fernandez, a highly experienced scientist with outstanding track record of publications and mentorship, will guide the candidate through the duration of the award and instruct him in instrument development required to set up assays of bacterial attachment under force. Progress will be monitored by an Advisory Committee composed of two independent professors and Prof. Fernandez. The candidate will keep up to the expectations of the K99/R00 award, as shown by previous accomplishments in the form of high-impact papers, fellowships, awards, and oral presentations at international conferences.